TOPEX POSEIDON ORBIT ERROR ASSESSMENT

This paper discusses the accuracy of TOPEX/Poseidon orbits computed at Delft University, Section Space Research & Technology (DUT/SSR&T), fr om several types of tracking data, i.e. SLR, DORIS, and GPS. To quanti fy the orbit error, three schemes are presented. The first scheme reli es on the direct altimeter observations and the covariance of the JGM- 2 gravity field. The second scheme is based on crossover difference re siduals while the third scheme uses the differences of dynamic orbit s olutions with the GPS reduced-dynamic orbit. All three schemes give co mparable results and indicate that the radial orbit error of TOPEX/Pos eidon is 3-4 cm. From the orbit comparisons with GPS reduced dynamic, both the along-track and cross-track errors of the dynamic orbit solut ions were found to be within 10-15 cm.